Technical Field
The present invention relates to an exposure control technique suitable for improving a quality of video data of a partial area sampled from entire video data.
Description of Related Art
A network camera has been known as one example of a conventional imaging apparatus. Such a network camera is used for a TV conference system, a monitoring system, and the like, and has a pan-tilt-zoom (PTZ) function for photographing an entire video image of a photographing target and a background. The network camera has a driving mechanism that changes the optical axis direction of a camera lens in up and down and right and left directions to achieve the pan-tilt function, and an optical mechanism that changes a magnification to achieve a zoom function.
In recent years, a resolution of an image sensor has been enhanced and also a digital signal process (DSP) technique has been remarkably progressed. In the recent network camera, the pan-tilt function is achieved by not an optical mechanism but a digital process to a partial area sampled by scrolling entire video data photographed by a wide-angle lens. A zoom function is also achieved by not an optical mechanism but a digital process.
A digital pan-tilt-zoom function is achieved with a signal process technique for the network camera for use in a TV conference system and the like by performing the most suitable exposure control to entire video data photographed by the wide-angle lens, sampling video data of a required partial area from the entire video data, and enlarging the sampled video data of the partial area with a predetermined digital zoom process.
Japanese Laid-Open Patent Application No. 2003-107555 discloses an imaging apparatus capable of appropriately exposing a target figure regardless of a position and an area of a figure in a screen.
When the video data of the partial area is sampled by scrolling the entire video image with the pan-tilt operation, the video data of the partial area is actually displayed on the monitor. A level of such video data differs depending on an area, for example, such video data may be too dark or too bright. For this reason, a user feels discomfort depending on the video data of the partial area when the user confirms such video data. This is caused by performing the most suitable exposure control only to the entire video data photographed with the wide-angle lens.